192 BOTANICAL GAZETTE | [SEPTEMBER 
In order to determine whether a correlation existed between 
the lateral halves of the leaf and the costal region in the produc- 
tion of protonemata, the lateral halves of a series of leaves were 
separated from the costal regions, and both retained in culture. 
Under no conditions were the cells or the lamina able to grow 
out into protonemata, the cultures being kept several months 
without any sign of growth. The costal portions after the usual 
length of time showed a growth of protonemata in the ordinary 
way, only the number was greatly reduced. The cells of the 
lamelle are not able to grow out into protonemata, neither when 
in connection with the leaf nor when separated. The power of 
regeneration is thus distinctly localized in the large cells of the 
costa lying at the base of the outer lamellz. 
Whole plants which were kept under exactly the same con- 
ditions as the detached leaves gave rise to no protonemata from 
the leaves. That the production of protonemata was not called 
forth by cutting was shown by the experiments in which half of 
the leaf tip was cut away while the outer half was left in con- 
nection with the stem. Under these conditions the portion of 
the leaf remaining in connection with the stem showed no 
growth. A complete separation of the leaf from the stem is 
then necessary to call forth the power of the leaves to produce 
rot ta and buds. 
The defoliated stems of Atrichum when placed under con- 
ditions favorable to growth gave rise to new shoots as axillary 
branches. This regeneration by means of new side branches 
occurred as readily in darkness as in light. In the dark the 
shoots grew more rapidly, producing more slender stems with 
reduced leaves. The tendency to apical production of shoots 
was not well marked, the shoots appearing at various points 
along the stem from base to apex. No new production of 
rhizoids or protonemata was obtained from the stems under any 
conditions, although the cultures were kept for several months. 
Whole plants under exactly the same conditions as the defoliated 
stems produced new shoots as axillary branches but not in as 
great abundance as the defoliated stems, showing that the pro- 
duction is accelerated by defoliation. 
